单选题 A nurse instructs a prenatal class about the importance of doing Kegel exercises frequently. Kegel exercises help to（）

A、 promote better breathing by strengthening the diaphragm muscle.
B、 maintain good perineal muscle tone by tightening the pubococcygeus muscle.
C、 minimize leg cramps by strengthening the calf muscles.
D、 prepare the mother for pushing by strengthening the abdominal muscles.

【正确答案】 B

【答案解析】Kegel exercises are performed by alternately tightening and releasing perineal muscles to strengthen the pubococcygeus muscle and increase its elasticity. The pubococcygeus muscle supports internal organs, such as the uterus and bladder. Kegel exercises don’t affect breathing or muscles of the diaphragm, leg, or abdomen.